CN101601203B - Method and apparatus for transmitting frames across a communication network - Google Patents

Abstract

A method and apparatus include a scheduling entity ( 208 ) for selecting a coding scheme and transmitting the frame ( 304 ) across a communication network ( 100 ). The controller ( 206 ) coupled to scheduling entity ( 208 ) determines a transmission gain for the frame based on the received signal interference and assigned reliability factor for the communication node. The scheduler entity ( 208 ) selects the lowest coding scheme for the frame corresponding to the determined transmission gain. The transceiver ( 214 ) coupled to controller ( 206 ) via interface ( 212 ) receives the encoded frame and transmits the frame to a plurality of mobile stations in the communication network ( 100 ).

Description

Method and apparatus for transmitting frames over a communication network

technical field

The present invention relates generally to selecting a coding scheme and transmitting frames over a communication network, and more particularly to transmitting frames with a repetition rate based on transmit gain.

Background technique

Wireless communication systems provide two-way communication between a plurality of fixed or portable subscriber units and a fixed network infrastructure such as base stations or access points. Fixed network infrastructure uses channel control information to establish links for two-way communication. Channel control information is transmitted as part of a frame through the wireless communication system. Since the channel control information contains information necessary for establishing and maintaining communication in a wireless communication system, the channel control information occupies a considerable portion of the frame. Thus, channel control information reduces the amount of space in a frame that can be used to transmit user data.

In current systems, a base station receives channel quality information (CQI) from a subscriber station and thus classifies the subscriber station into different groups. The base station encodes and transmits channel control information based on the group of subscriber stations. In general, two types of channel control information are sent from the base station to the subscriber station. The first channel control information is sent to all subscriber stations in the cell regardless of the group of subscriber stations. The second channel control information is sent to all subscriber stations individually in groups. The base station assigns coding schemes based on groups of subscriber stations. The subscriber station's grouping is updated based on the channel quality information after a predetermined time interval. However, channel quality information may change frequently within predetermined time intervals, and thus may not be reflected on packets of subscriber stations. Therefore, the assigned coding scheme may not be suitable for the channel conditions during the predetermined time interval. Furthermore, the process of updating the grouping of subscriber units is a complex process and requires much additional messaging for grouping/tracking subscriber units in the communication network. Therefore, the efficiency of the channel and the reliability factor of the communication node are reduced.

Therefore, there is a need for more efficient transmission of channel control information over communication networks.

Description of drawings

In the drawings, like reference numbers indicate identical or functionally similar elements in the various independent views, and the accompanying drawings, together with the following detailed description, are incorporated into and form a part of this specification to further illustrate various implementations example, and serves to explain all of the various principles and advantages according to the present invention.

Figure 1 is a block diagram of a wireless communication network according to some embodiments of the invention;

Figure 2 is a block diagram of a communication node according to some embodiments of the invention;

Fig. 3 is the structure of the frame according to some embodiments of the present invention;

4 is a flowchart of a method for transmitting a frame over a communication network according to some embodiments of the invention;

5 is a flowchart of a method for selecting a coding scheme and transmitting frames over a communication network according to some embodiments of the invention;

Those skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.

Detailed ways

Before describing in detail embodiments according to the present invention, it should be noted that the embodiments pertain primarily to selecting a coding scheme and transmitting frames over a communication network. Accordingly, conventional notation has been used where appropriate to indicate apparatus and method components in the drawings showing only those specific details that are relevant to the understanding of the embodiments of the invention so as not to obscure the The descriptions herein may obscure details that would be apparent to those skilled in the art.

In this document, relational terms such as first and second, top and bottom, etc. may be used only to distinguish one entity or action from another without necessarily requiring or implying a relationship between such entities or actions. Any actual such relationship or order. The term "comprising" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article or apparatus comprising a series of elements includes not only those elements, but may also include processes, methods, articles not expressly listed or such or other elements inherent to the device. An element introduced by "comprising a" does not, without more qualifications, exclude the presence of additional identical elements in the process, method, article, or apparatus comprising that element.

It should be understood that embodiments of the invention described herein may include one or more conventional processors and uniquely stored program instructions controlling the one or more processors to implement the described herein in conjunction with certain non-processor circuitry The function of selecting a coding scheme and transmitting frames on a communication network for some, most, or all of them. Non-processor circuits may include, but are not limited to, radio receivers, radio transmitters, signal drivers, clock circuits, power supply circuits, and user input devices. In this regard, these functions may be interpreted as steps to perform a method of selecting a coding scheme and transmitting frames over a communication network. Alternatively, some or all of the functions may be implemented by a state machine without any stored program instructions, or in one or more application specific integrated circuits (ASICs), where each function or some combination of certain functions are implemented as custom logic. Of course, a combination of both approaches can be used. Accordingly, methods and apparatus for these functions have been described herein. Furthermore, it is expected that those skilled in the art, when guided by the concepts and principles disclosed herein, will readily Such software instructions and programs and ICs can be generated with minimal experimentation.

Various embodiments are disclosed herein. For example, a method for selecting a coding scheme for a frame in a communication node includes assigning the communication node a reliability factor and determining signal interference associated with a mobile station. The method also includes determining a transmit gain to reduce signal interference, wherein the transmit gain is based on the determined signal interference and the assigned reliability factor for the communication node. The method further includes selecting a coding scheme to obtain a transmit gain for a frame to be transmitted to the mobile station.

Another embodiment includes a communication node for selecting a coding scheme for a frame. The communication node includes a transceiver for transmitting and receiving a signal, wherein the signal consists of a plurality of frames and includes signal interference, and a controller coupled to the transceiver. The controller determines a transmit gain for transmitting signals, and wherein the transmit gain is based on a reliability factor and received signal interference. A scheduler coupled to the controller is used to select a coding scheme to obtain a transmit gain for frames to be transmitted by the transceiver.

In an embodiment, a method for selecting a coding scheme for a frame in a communication node includes assigning the communication node a reliability factor, and receiving a Carrier to Interference and Noise Ratio (CINR) from a mobile station. The method also includes determining a transmit diversity gain in response to the received CINR and the assigned reliability factor. The method further includes selecting a repetition rate for frames based on the determined transmit diversity gain.

FIG. 1 illustrates a block diagram of a wireless communication network referred to hereinafter as communication network 100 . The communication network 100 includes a communication node 102 and a plurality of mobile stations 104-112 located at various locations around the communication node 102. Communication node 102 and mobile stations 104-112 are configured to operate according to any of a number of different 2G, 3G and 4G technologies. These technologies include GSM, CDMA, UMTS, CDMA2000, W-CDMA, OFDM, and others. Likewise, communication nodes and mobile stations in other communication networks are configured to operate according to different radio technologies. Adjacent communication networks can operate using the same wireless technology. The communication node 102 may also communicate with other communication nodes and with mobile stations using IEEE-802.16 based metropolitan area networks. Different wireless protocols can use the principles of the invention.

In an embodiment, the communication node 102 may be a base station, access point, access router, or the like. Communication node 102 provides wireless broadband access to mobile stations 104-112 within the coverage area of communication network 100. Mobile stations 104-112 can use the broadband network to access voice, data, video, video teleconferencing, and/or other broadband services. Mobile stations 104-112 may be any of a number of mobile devices, including wireless-enabled laptop computers, personal data assistants, notebooks, handheld devices, cellular telephones, personal computers, personal digital assistants, or other wireless-enabled devices. Additionally, although only five mobile stations 104-112 are depicted in FIG. 1 to avoid cluttering the figure, it should be understood that the communications network 100 may provide wireless broadband access to more or fewer mobile stations.

In operation, sending a data message to a mobile station by the communication node 102 is referred to as a downlink communication. Similarly, sending a data message by a mobile station to the communication node 102 is referred to as an uplink communication. The data messages may be referred to as packets, variable-sized data units, or frames. The frame includes a Medium Access Protocol message (MAP) used as channel control information for assigning a channel to the mobile station.

In the embodiment of FIG. 1, communication node 102 is capable of communicating with each of mobile stations 104-112. A mobile station determines channel conditions associated with it. Channel conditions include carrier-to-interference-plus-noise ratio (CINR), signal-to-noise ratio (SNR), or frame error rate (FER). The determined channel conditions may be further transmitted to the base station via a feedback channel. The base station collects channel conditions associated with each mobile station, and thus determines signal interference in each channel. Signal interference indicates the amount of errors that may occur in a frame. The transmit gain required for a frame to arrive at the mobile station with a reduced error rate is determined by the received signal interference.

Figure 2 is a block diagram of a communication node 200 according to some embodiments of the invention. In an embodiment, the transceiver 214 communicates over the communication network via at least one antenna 218 . Controller 206 and transceiver 214 communicate via interface 212 . In particular, controller 206 , coupled to processor 204 , submits to transceiver 214 fixed or variable sized units of data, cells or packets, collectively referred to as "frames." Transceiver 214 further transmits the received frames to a plurality of mobile stations. Controller 206 may also transmit user data frames, management frames, and other data directly to transceiver 214 . The controller 206 submits to the scheduler 208 of the communication node 200 the transmit gain required for the frame for reliability of assignment with reduced error rate. In addition, the transceiver 214 receives an encoded frame from the controller 206 and transmits the frame over the communication network according to the parameters within the frame. Transceiver 214 also receives frames of information from the mobile station via antenna 218 and provides the received frames to controller 206 via interface 212 . Transceiver 214 may also report status information to controller 206 . For example, the status information may include an indication of whether a frame has been successfully transmitted. A user interface is coupled to the controller for assigning a reliability factor to the communication node. The reliability factor may be a measure of the acceptable percentage of frames that were transmitted error-free to multiple mobile stations. The reliability factor may be assigned by an operator in the communication node through a user interface coupled to the controller.

The specific configuration and implementation of controller 206 depends on the type of communication network, its data transmission bandwidth, and the type and amount of information being processed. Furthermore, in the embodiment of communication node 200, controller 206 and scheduler 208 operate as a management and frame scheduling entity that coordinates with other network-attached devices such as mobile stations, access points, base stations, etc. Function.

In an embodiment, the communication node 200 uses a transceiver 214 coupled to the interface 212 and receives channel condition information associated with a mobile station. The channel condition information may be FER, CINR or SNR for the frame. The channel condition information is forwarded to controller 206 via interface 212 . Controller 206 then processes the channel condition information and determines signal interference in the channel. Additionally, the controller may also receive a reliability factor assigned by an operator via a user interface. The controller further determines a transmit gain required for the frame to be transmitted to the mobile station. After this, the signal interference is compensated in order to obtain the reliability factor assigned to the communication node. The transmit gain may be the transmit diversity gain of the antenna. A calculation is made on the probability distribution function of the antenna to determine the transmit gain. Transmit diversity gain can be obtained via antenna arrays, smart antennas, multiple-input and multiple-output (mimo) antennas, or broadcast antennas. Different diversity techniques are used to determine transmit gain. For example, using Transmit Adaptive Array-Maximum Ratio Transmit (TxAA-MAT) transmit diversity, a transmit gain of 7db is obtained. Similarly, using transmit adaptive array-eigenbeamforming (TxAA-EBF) transmit diversity, a transmit gain of 6 db is obtained, and using Alamouti transmit diversity, a transmit gain of 1 db is obtained.

Additionally, controller 206 forwards the determined transmit gain to scheduler 208 . Scheduler 208 selects a coding scheme for the frame based on the determined transmit gain. The encoding scheme may include assigning repetition rates for media access protocol messages in the frame. This repetition rate is kept as low as possible in order to obtain a reliability factor for the communicating nodes and also to obtain the lowest error rate for the frames.

In an embodiment, processor 204 coupled to controller 206 maps external network data to access control data. The access control data may be a Media Access Controller Service Data Unit (MAC SDU). Processor 204 forwards the access control data to controller 206 . The controller 206 receives access control data strings, and converts each access control data into frames by adding necessary header information. The frame may be a MAC Packet Data Unit (PDU). In addition, the controller 206 may also manage the buffering of frames. Frames with the necessary header information are forwarded to the scheduler 208 . The scheduler 208 receives frames and determined transmit gains for each frame from the controller. The scheduler is provided with a look-up table with different predefined coding schemes for various transmit gains. The coding scheme may be the repetition rate required for the frame. The scheduler 208 selects a coding scheme for the determined transmit gain from among a plurality of coding schemes stored in the look-up table 210 . The lookup table 210 may be part of the scheduler, or it may be found elsewhere in the communication system 100 . Thus, the selected coding scheme will be the coding scheme required for frames transmitted with a reduced error rate for the assigned reliability factor. Finally, the frame is encoded by the selected encoding scheme and transmitted to the mobile station. This process is repeated for all frames and all channels associated with the mobile station.

FIG. 3 shows the structure of a frame according to an embodiment of the present invention. The communication node 102 uses frame strings 302-310 for allocating channels to mobile stations. Each of frames 302-310, eg, frame 304, includes a Medium Access Protocol (MAP) message 314 for allocating a channel to the mobile station. The MAP message 314 is encoded such that it can be decoded by one of the mobile stations 104-112 with the worst signal quality. However, this can cause a large amount of process redundancy in the downlink MAP and uplink MAP, thereby significantly increasing the overhead. This process redundancy is necessary for mobile stations 104-112 with poor signal quality, but not for other mobile stations. Therefore, in accordance with the principles of the present invention of varying the coding scheme between frames based on various criteria, the scheduler 208 uses a simple repetitive coding technique that can reduce channel overhead by determining the coding scheme.

Repetition coding techniques are processes in which multiple transmission symbols in a frame are repeated multiple times. In an embodiment of a WiMAX network, a transmission symbol may be referred to as a slot, which is a combination of a time symbol and a frequency tone. Slots can be grouped together to form the MAP and user data portions of a frame. The MAP part, called a MAP message, undergoes repetition encoding techniques. In another embodiment, repetition coding may also be applied to the user data portion.

In an embodiment, the MAP message in the frame is repeated multiple times depending on the received signal interference in the channel and the reliability factor assigned to the communication node. The number of times the MAP message is repeated is represented by the repetition factor or repetition rate of the frame. In one embodiment, the scheduler allows simple repetition encoding techniques to be used on MAP messages 314 in addition to basic encoding techniques. The basic encoding technique can be Quadrature Phase Shift Keying (QPSK), Binary Phase Shift Keying (BPSK) or other encoding techniques. In another embodiment, different coding techniques such as changing the coding rate or modulation order can also be applied. For example, a frame may be encoded using a QPSK frame, a 16-QAM frame, or a 64-QAM frame.

In the embodiment of FIG. 3 , frame 304 has a frame channel header (FCH) 312 , at least one MAP message 314 and a user data portion 316 . The MAP message 314 may be a downlink MAP (DL-MAP) or an uplink MAP (UL-MAP). FCH 312 indicates the repetition rate for the frame. The frame may also contain other data not shown in Figure 3 but not required for understanding the invention. Frame 304 may be 5 ms in duration and may have a varying repetition rate. The repetition rate of the frame may vary according to the determined transmit gain for the frame. A high repetition rate can reduce the frame error rate. However, this may not result in a reliability factor assigned to the correspondent node. For example, a mobile station requiring a 2x repetition rate can easily decode a frame with a 4x repetition rate without error, but transmitting a frame with a 4x repetition rate can reduce the reliability factor for the communication node. Therefore, the lowest possible repetition rate is chosen for this frame in order to obtain a reliability factor for the communicating node with a reduced error rate. Since the FCH sent before the MAP message indicates the type of repetition rate used for the frame, repetition coding can be applied to any type of communication network without making any changes to the standard.

As in the example shown in FIG. 1 , five mobile stations 104 - 112 are operating in the communication network 100 . Since the mobile station 104 has good channel conditions, the mobile station 104 can decode the MAP message in the frame with a repetition rate of 1x. Mobile station 106 may decode a MAP message with a 2x repetition rate; mobile station 108 may require a 3x repetition rate to decode a MAP message without any errors; mobile station 110 may require a 4x repetition rate, and mobile station 112 may require a 5x repetition rate. The repetition rate may be based on the relative channel condition strength for the best channel condition with the lowest rate and the worst channel condition with the highest rate. MAP messages may be transmitted to mobile stations 104-112 using frame strings 302-310 of FIG. Mobile station 104 may decode any of frames 302-310 with a repetition rate of 1x or higher. The mobile station 106 can decode frames with a repetition rate of 2x or higher. Similarly, mobile station 112 may decode frames at a repetition rate of 5x or higher. Therefore, the lowest repetition rate for each frame is selected based on the signal interference in the channel and the reliability factor assigned to the communication node.

The scheduler 208 selects a repetition rate from a plurality of repetition rates stored in a lookup table. The repetition rate selected for a frame corresponds to the determined transmit gain for that frame. Signal interference can be compensated for a certain transmission gain in order to obtain a reliability factor for the communication node. For example, mobile station 108 requires a repetition rate of 3x to receive frames without errors. However, choosing a 3x repetition rate for this frame may reduce the reliability factor. Therefore, the next lowest 2x repetition rate may be selected by the scheduler 208 in order to obtain a reliability factor and transmit frames with a reduced error rate. Similarly, mobile station 106 may require a repetition rate of 2x to decode frames without any errors. The frame can be transmitted with a higher repetition rate of 3x, 4x or 5x. Transmitting frames with a higher repetition rate can reduce the error rate, but may require higher transmit gain, which in turn reduces the reliability factor of the communicating node. Therefore, a repetition rate of at least 2x is chosen to obtain a reliability factor and transmit the frame with a reduced or no error rate.

Figure 4 is a flowchart illustrating a method for transmitting a frame over a communication network. A communication node receives a reliability factor assigned by an operator in the communication node (401). A communication node establishes (402) connections with a plurality of mobile stations in a communication network. In another aspect, the communication node determines (404) signal interference associated with the mobile station. Signal interference is determined based on channel conditions received from the mobile station. Channel conditions include carrier-to-interference-plus-noise ratio (CINR), signal-to-noise ratio (SNR), or frame error rate (FER). The controller determines (406) a transmit gain based on the signal interference and the assigned reliability factor for the communication node. The transmit gain may be a transmit diversity gain of the antennas to transmit frames with a reduced error rate for an assigned reliability factor. The controller further forwards (408) the determined transmit gain to the scheduler. A scheduler in the communication node selects (410) for a frame a coding scheme corresponding to the determined transmit gain for that frame. The selected coding scheme may be one of a plurality of coding schemes stored in a look-up table of the scheduler, or may be a coding scheme determined by another method based on transmit gain. Finally, the frame is encoded (412) by the selected one of the plurality of encoding schemes and transmitted (414) to the mobile station in the communication network.

FIG. 5 is a flowchart illustrating the process by which the scheduler selects an encoding scheme for a frame and encodes the frame accordingly, eg, steps 408-414 of FIG. 4 . A scheduler of a communication node receives (502) a string of frames from a controller. The scheduler obtains (504) a frame from the frame string and selects the lowest encoding scheme for that frame. This means, for example, selecting the lowest repetition rate from the repetition rates stored in the look-up table in steps 506, 512, 518 of FIG.

For example, the scheduler selects (506) for a frame a repetition rate of 1x for the frame. The scheduler further checks (508) to see if the selected repetition rate corresponds to the determined transmit gain. In other words, the transmit gain required for a frame with a repetition rate of 1x is within the determined transmit gain. The transmit gain may be a transmit diversity gain of the antennas to transmit frames with a reduced error rate for an assigned reliability factor. If the repetition rate corresponds to transmit gain, the frame is encoded (510) with the selected repetition rate of 1x. If the repetition rate of 1x does not correspond to the determined transmit gain, then the next higher repetition rate of 2x is selected (512). The selected 2x repetition rate is further checked (514) to see if the 2x repetition rate corresponds to the determined transmit gain. If a repetition rate of 2x corresponds to transmit gain, the frame is encoded with the selected repetition rate. If the repetition rate does not correspond to transmit gain, the scheduler selects the next higher repetition rate. This continues until the lowest repetition rate corresponding to the determined transmit gain is selected. The same process is repeated for all frames in the string. Finally, the encoded frames are transmitted to a plurality of mobile stations in the communication network.

In another embodiment, a mobile station receives a frame transmitted by a communication node. The mobile station determines the frame repetition rate by means of the Frame Channel Header (FCH), which is sent before the Medium Access Protocol (MAP) message. Since the FCH indicates the repetition rate used for the frame, frames with any repetition rate can be transmitted regardless of the communication network's standard. Since the selection of the repetition rate for the frame depends on the transmit gain for the frame, which in turn depends on the signal interference and the assigned reliability factor, the mobile station collects the MAP messages in repeated frames and uses acceptable error or signal loss to reconstruct the frame.

In the foregoing specification, specific embodiments of the invention have been described. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of this invention. Benefits, advantages, and solutions to problems, and any element(s) that would cause any benefit, advantage, or solution to occur or become more apparent, should not be construed as critical, A required or necessary characteristic or element. The invention is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued.

Claims (10)

1. be used to frame to select a method for encoding scheme, comprise:

For the communication node assignment reliability factor, wherein, described reliability factor is to being launched into error-free the tolerance of the percentage accepted of the frame of a plurality of mobile radio stations;

The signal that mobile radio stations definite and in described a plurality of mobile radio stations are associated disturbs;

Determine that transmitting gain disturbs to reduce described signal, wherein, described transmitting gain disturbs based on described definite signal and is the reliability factor that described communication node is assigned; And

Select encoding scheme, to obtain for being sent to the described transmitting gain of frame of a described mobile radio station of described a plurality of mobile radio stations, wherein, the frame of selecting encoding scheme to be included as will to be sent out selects lowest repetition rate to obtain the described reliability factor for described communication node.

2. method according to claim 1, wherein, determine that described transmitting gain further comprises, select the type for the antenna of described communication node, and wherein, described transmitting gain is the emission diversity gain of described antenna, with the reliability factor for described appointment, with the error rate reducing, sends described frame.

3. method according to claim 1, wherein, select described encoding scheme further to comprise, utilize look-up table to choose the minimum encoding scheme for described definite transmitting gain, described minimum encoding scheme is of a plurality of encoding schemes in described look-up table.

4. method according to claim 1, further comprises:

By utilizing the encoding scheme of the described selection described frame of encoding; And

The frame of described coding is transmitted into the described mobile radio station in described a plurality of mobile radio station.

5. a communication node, comprising:

Transceiver, described transceiver is used for transmitting and receiving signal, and wherein, described signal is comprised of a plurality of frames and comprises that signal disturbs;

Controller, described controller is coupled to described transceiver, wherein, the transmitting gain that described controller is identified for transmitting, and wherein, described transmitting gain disturbs based on reliability factor and the signal that receives, and wherein, described reliability factor is to being launched into error-free the tolerance of the percentage accepted of the frame of a plurality of mobile radio stations; And

Scheduler, described scheduler is coupled to described controller, for selecting encoding scheme with the described transmitting gain of the frame that obtains being launched by described transceiver, wherein, the frame of selecting encoding scheme to be included as will to be launched selects lowest repetition rate to obtain the described reliability factor for described communication node.

6. communication node according to claim 5, wherein, described scheduler further comprises that storage is for the look-up table of the different encoding schemes of the described frame of encoding.

7. communication node according to claim 6, wherein, chooses the minimum encoding scheme corresponding to described definite transmitting gain in the different encoding schemes of described scheduler from described look-up table.

8. for a method for communication node, comprising:

For the described communication node assignment reliability factor, wherein, described reliability factor is to being launched into error-free the tolerance of the percentage accepted of the frame of a plurality of mobile radio stations;

A mobile radio station reception carrier from described a plurality of mobile radio stations with interference plus noise than (CINR);

Reliability factor in response to the described CINR receiving and described appointment is determined emission diversity gain; And

Based on described definite emission diversity gain, come to select lowest repetition rate for frame.

9. method according to claim 8, wherein, determines that described emission diversity gain further comprises the probability-distribution function that calculates antenna, to obtain the described emission diversity gain for the reliability factor of described appointment.

10. method according to claim 8, wherein, determines that described emission diversity gain further comprises: the CINR receiving described in the described transmission diversity gain by changing antenna compensates for the reliability factor of described appointment.